Dependence of Soil Organic Matter and Plant Residues Decomposition on Temperature and Moisture in the Long-Term Incubation Experiments

Temperature and moisture are the main external factors controlling organic matter decomposition and mineralization in soil. The effect of temperature (8 and 22 degrees C) and moisture (15, 30, and 45 mass %) of gray forest soil (Luvic Retic Greyzemic Phaeozems (Loamic)) on decomposition of tree residues (leaves, small twigs, thin roots) and agricultural plants (clover aboveground mass and roots, barley straw and roots) has been studied in two long-term experiments. Coarsely crushed (10-2 mm) plant residues were added to the soil in dry form in an amount of 1% of the soil mass. The decomposition of soil organic matter and plant residues were assessed by the quantification of C-CO2 emitted from the soil. The efficiency and rate of decomposition of soil organic matter and plant residues depended on the type of decomposed material rather than on the temperature and moisture levels. The predominant decomposition of easily decomposable components hid the temperature response of stable compounds and low-quality plant residues. The slowly decomposable plant residues were more sensitive to soil wetting. Temperature coefficients Q(10) of mineralization of soil organic matter and plant residues were on average 1.66 +/- 0.41 and 1.39 +/- 0.06, respectively. Moisture coefficients W-10 in the gravimetric moisture intervals of 15-30 and 30-45% were 1.22 +/- 0.09 and 1.21 +/- 0.05 for soil and 1.29 +/- 0.20 and 1.25 +/- 0.13 for plant residues respectively.